March 30, 2012 — Prenatal exposure to common urban air pollutants
known as polycyclic aromatic hydrocarbons (PAHs) may lead to
behavioral problems, including poor attention, anxiety, and depression,
in young children, new research suggests.
In a follow-up study of children from the Columbia Center for
Children's Environmental Health (CCCEH) cohort study, those who had
prenatal exposure to PAHs were significantly more likely to have
attention problems and symptoms of anxiety and depression by the age of 6
to 7 years than children who were not exposed to high levels of the
pollutants.
Exposure levels were measured in both monitored air concentrations of
PAH and a PAH biomarker assessed in maternal and umbilical cord
blood.
"This study provides new evidence that prenatal exposure to air
pollution at levels encountered in New York City adversely affects child
behavior," principal investigator Frederica Perera, DrPH, professor
at the Mailman School of Public Health at Columbia University in New
York
City and director of the CCCEH, told Medscape Medical News.
Dr. Frederica Perera
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"The results are of concern because attention problems and anxiety
and depression have been shown to affect children's academic
performance and their relationships with peers," said Dr. Perera.
The study was published online March 22 in Environmental Health Perspectives.
Crosses the Placenta
PAHs are a common urban air pollutant that result from the incomplete
combustion of fossil fuels, including diesel fuel, gasoline, oil used
for heating purposes, and coal.
When inhaled by the mother during pregnancy, PAHs can be "transferred
across the placenta" and bind to a fetus' DNA, forming adducts in
blood and other tissues, according to the investigators in a release.
The ongoing CCCEH study originally enrolled 536 nonsmoking inner-city
pregnant women who were between the ages of 18 and 35 years. All were
black or Dominican-American.
"When we started this study over 12 years ago, there was little
information on the role of prenatal exposures on later child health and
developmental outcomes. So we decided to mount a study that was quite
detailed in attempting to measure and record as many environmental
exposures as we could," explained Dr. Perera.
"We included women who were nonsmokers because we did not want to be
influenced by active smoking, which is a known risk factor for the
outcomes of concern. Many were exposed to second-hand smoke, but we
adjusted and controlled for that, as well as for lead and pesticides."
She noted that all of the participants were from the Northern
Manhattan area of Washington Heights in New York City, where black and
Dominican-American individuals make up the majority of the population.
Small backpack monitors measured the air to which the women were
personally exposed during pregnancy. High levels of prenatal PAH
exposure were defined as levels greater than 2.27 ng/m3.
DNA adducts specific to benzo[a]pyrene, a representative PAH, were also measured in both maternal and cord blood.
The children, who were born between 1999 and 2006, have been periodically assessed since birth.
Previously, the investigators published findings
showing that prenatal exposure to PAH was associated with
developmental delays by the time these children were 3 years of age. The
researchers also found, as reported in Pediatrics, that the cohort was more likely to have reduced IQ by the age of 5 years.
Behavioral Symptoms
For this analysis, the researchers sought to examine 253 of the offspring when they were between the ages of 6 and 7 years.
The Child Behavior Checklist (CBCL) was administered to the mothers
to assess behavioral symptoms of anxiety/depression and attention
problems in their children. CBCL scales derived from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition
(DSM-IV) were also used to measure anxiety and to assess for problems
associated with attention-deficit/hyperactivity disorder (ADHD).
An investigator-administered questionnaire was also given to the
mothers during the last trimester of pregnancy, at 6 months after giving
birth, and annually after that. The questionnaire collected
information on demographics, health, environment, and dietary PAH (which
can include broiled, grilled, smoked, or fried meat).
Results showed that all of the mothers had detectable levels of PAH in their personal air samples.
However, children who were exposed to high levels of prenatal PAH, as
shown on maternal personal air monitoring, had significantly higher
adjusted scores for anxiety/depression (P < .0001) and for attention problems (P = .001) than children exposed to lower levels.
They also had significantly more DSM-IV-oriented anxiety problems (P = .009). There were no significant between-group differences in DSM-IV-oriented ADHD problems.
After adjusting for the summary scores of other environmental
exposures measured (including bisphenol A, chlorpyrifos, and
phthalates), the link remained significant between PAH and increased
CBCL scores for anxiety/depression and attentional problems.
This link was also significant with regard to high vs low levels of PAH adducts in maternal blood (P = .019 for increased anxiety/depression scores; P = .003 for increased attention problems), as well as in cord blood (P < .001 for anxiety/depression scores; P = .002 for attention problems).
Need for Awareness
Dr. Perera reported that the investigators will continue following these children until they reach the age of 12 years.
"We hope to follow them right up through adolescence in order to get a
full understanding of what the potential effects of these exposures
might be, what emerges over time, and possible reversibility."
She suggested that parents living in urban settings should also be
aware of their indoor environment. Steps could include not allowing
people to smoke in the home, ventilating with a fan when cooking,
avoiding exposure to other chemicals such as pesticides, and
incorporating a healthy diet rich with fruits and vegetables. Other tips
are available on the CCCEH Web site.
"I think clinicians should be aware of the information about these
environmental pollutants and should provide helpful tips to their
patients," concluded Dr. Perera.
The study was supported by the Educational
Foundation of America, the John and Wendy Neu Family Foundation, the New
York Community Trust, and Trustees of the Blanchette Hooker Rockefeller
Fund, and by grants from the National Institute of Environmental Health
Sciences and the US Environmental Protection Agency.
Environ Health Perspect. Published online March 22, 2012. Abstract
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